1. Power off device
2. Go to recovery mode (power+home+volume up)
3. Wipe cache partition
4. Wipe data/factory reset
5. Then click reboot system
6. Suddenly go to download mode (power+home+volume down) while
Device is Restarting
7. Use Odin 3.10.7...
Just done it about a month ago on my E5, No risk at all and I downgraded successfully to KitKat from Lollipop. Just download the KitKat firmware and flash it via Odin, just make sure after flash that you boot to recovery and perform full data wipe...